How To Test Backup Copy (Replication) Speed

SUMMARY

By using tools such as iperf and iptraf we can test the over all speed of backup copy (replication).

ISSUE

How to test replication bandwidth throughput. 

RESOLUTION

On the target, run iperf in server mode:

[[email protected] ~]# iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------

Test a source that is across a VPN connection. The following iperf command options will be used:
-P = number of parallel client threads to run
-r = Do a bidirectional test individually
-i = pause n seconds between periodic bandwidth reports
-t = time in seconds to transmit for (default 10 secs)

To test the source, run the following command:
[[email protected] ~]# iperf -c targetVM -P 4 -r -i 10 -t 120
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to UnitrendsVM, TCP port 5001
TCP window size: 96.7 KByte (default)
------------------------------------------------------------
[  6] local 192.168.0.251 port 55062 connected with 192.168.0.11 port 5001
[  7] local 192.168.0.251 port 55064 connected with 192.168.0.11 port 5001
[  8] local 192.168.0.251 port 55063 connected with 192.168.0.11 port 5001
[  5] local 192.168.0.251 port 55061 connected with 192.168.0.11 port 5001
[ ID] Interval       Transfer     Bandwidth
[  6]  0.0-10.0 sec   267 MBytes   224 Mbits/sec
[  8]  0.0-10.0 sec   267 MBytes   224 Mbits/sec
[  5]  0.0-10.0 sec   268 MBytes   225 Mbits/sec
[  7]  0.0-10.0 sec   268 MBytes   225 Mbits/sec
[SUM]  0.0-10.0 sec  1.04 GBytes   897 Mbits/sec
[  6] 10.0-20.0 sec   265 MBytes   223 Mbits/sec
[  7] 10.0-20.0 sec   266 MBytes   223 Mbits/sec
[  8] 10.0-20.0 sec   266 MBytes   223 Mbits/sec
[  5] 10.0-20.0 sec   265 MBytes   223 Mbits/sec
[SUM] 10.0-20.0 sec  1.04 GBytes   891 Mbits/sec

This output shows us that our overall throughput is 1Gb, being this is a 1Gb NIC this is the correct transfer rate. Many times with openVPN, you will see the overall throughput significantly less than what the NIC is capable of. This is an indication that OpenVPN tuning maybe required. If you are replicating on the same network as your source, for example maybe you are looking to move the target to a new location and you want to replicate the initial seed on your faster connection. For this reason we suggest disabling the OpenVPN. In the step listed below you can test the UDP packets across the non-VPN to better determine if the issue is with OpenVPN requiring tuning or if the issue is network related.

To test a source connected via a non-VPN connection (ie, local network), the following iperf command option will be added:
-b = bandwidth set target bandwidth to n bits/sec (default 1 Mbit/sec).
While this setting requires UDP (-u), the -u flag is assumed and not required to add in your command.
 
[[email protected] ~]# iperf -c targetVM -P 4 -r -i 10 -t 120 -b 1000M
WARNING: option -b implies udp testing
------------------------------------------------------------
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size:  122 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to UnitrendsVM, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size:  122 KByte (default)
------------------------------------------------------------
[  5] local 192.168.0.251 port 43892 connected with 192.168.0.11 port 5001
[  3] local 192.168.0.251 port 55576 connected with 192.168.0.11 port 5001
[  8] local 192.168.0.251 port 51076 connected with 192.168.0.11 port 5001
[  4] local 192.168.0.251 port 35868 connected with 192.168.0.11 port 5001
[ ID] Interval       Transfer     Bandwidth
[  5]  0.0-10.0 sec   266 MBytes   224 Mbits/sec
[  3]  0.0-10.0 sec   268 MBytes   224 Mbits/sec
[  8]  0.0-10.0 sec   267 MBytes   224 Mbits/sec
[  4]  0.0-10.0 sec   263 MBytes   221 Mbits/sec
[SUM]  0.0-10.0 sec  1.04 GBytes   893 Mbits/sec
[  5] 10.0-20.0 sec   267 MBytes   224 Mbits/sec
[  3] 10.0-20.0 sec   267 MBytes   224 Mbits/sec
[  8] 10.0-20.0 sec   266 MBytes   223 Mbits/sec
[  4] 10.0-20.0 sec   266 MBytes   223 Mbits/sec
[SUM] 10.0-20.0 sec  1.04 GBytes   893 Mbits/sec

This output shows us that our overall throughput is 1Gb, being this is a 1Gb NIC this is the correct transfer rate. If it is below this, this may indicate the issue is on the network and not the Unitrends appliance. It is somewhat common for a firewall to have UDP flood protection, we suggest turning this feature off since a majority of our replication is sent over UDP.

On the source you can use iptraf to monitor the actual throughput eth0.  If your system does not have iptraf, it may be installed by running:
yum install iptraf

Once installed, run it:
iptraf
> Select Detailed interface statistics
> eth0

Monitor your outgoing rates, being this is all outbound traffic on eth0 we will notice a fluctuation in speed. If this is the first time replication is being sent to the target, keep in mind the target must hash the new backups therefore your total throughput maybe delayed as we are waiting for the target to complete the hash. Once the initial seed has been sent, we will only hash the changed blocks therefore increasing the replication throughput.
 

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